Rationale:

Maximal oxygen uptake (VO₂max) has defined the concept of exercise capacity and endurance performance for more than half a century. The concept of a plateau of VO₂ despite increasing muscle power output is a central tenant in the concept of VO₂max. Recently, the concept of VO₂max has been challenged, with suggestions that the plateau is more an artifact of testing procedures than of physiology.

Objectives:

This study was designed to compare VO₂ responses during sequentially administered exercise tests, with an increased workload during the second test, to evaluate the presence of a plateau of VO₂.

Methodology:

Competitive runners (6m,6f) performed incremental (3-min stages) treadmill exercise to fatigue, walked to recover for 3-min, then exercised for up to an additional 3-min at a faster pace (10.0 +/- 0.85 vs 11.0 +/- 0.85 mph).

Results:

During Run 1 the subjects did not consistently demonstrate criteria for a plateau of VO₂. However, comparing Run 1 vs Run 2, there were no significant (P <.05) difference in VO₂max (4.09 +/- 0.97 vs 4.03 +/- 1.16 L/min), V_Emax (126 +/- 29 vs 126 +/- 35 L/min), or HRmax (184 +/- 6 vs 181 +/- 10 bpm). There were significant differences in VCO₂max (4.40 +/- 1.08 vs 4.06 +/- 1.27 l/min) and RER (1.07 +/- 0.06 vs 1.00 +/- 0.06). There was some evidence of a differential effect for VO₂max in Run 1 vs Run 2 in males (4.97 +/- 0.41 vs 5.07 +/- 0.40 L/min) vs females (3.21 +/- 0.21 vs 2.99 +/- 0.46 L/min).

Conclusion:

The present data are supportive of the concept that VO₂ plateaus during successive heavy exercise bouts with an increase in workload, and as such supports the traditional concept of VO₂max.